BACTERIAL NUTRITION 383 



of Taylor (1902). It is not at all improbable that what Blumen- 

 thal reported as digestion was in reality only a solution of the 

 casein in an alkaline medium. 



THE UTILIZATION OF THE PRODUCTS OF WITTE's PEPTONE AND OF 

 CASEIN OBTAINED BY PARTIAL DIGESTION WITH TRYPSIN 



The inability of many organisms to develop in the common 

 laboratory media is due to the absence in these media of suffi- 

 cient food material which is immediately available for cell 

 nutrition. That a large part of Witte's peptone, as well as 

 gelatin, casein, unchanged native proteins and coagulated egg 

 albumin, is valueless as a source of organic nitrogen, in so far 

 as the large group of gelatin-non-liquefying organisms at least 

 is concerned, has been demonstrated in this investigation. 

 Smith (1897) pronounced plain peptone solution to be a poor 

 culture fluid. He stated that some organisms failed to grow in 

 Witte's peptone. Rivas (1912) found that short tryptic diges- 

 tion of peptone enhanced its value as a culture medium. Hot- 

 tinger (1913) who denounced Witte's peptone as unsatisfactory 

 for culture purposes suggested a pancreatic digestion product of 

 meat as a substitute. 



Dalimier and Lancereaux (1913) found the protein-free prod- 

 uct, ''opsine," which is rich in amino acids and other simple 

 nitrogenous substances, to serve as a good culture medium for 

 all of the many organisms studied, including some very fastid- 

 ious pathogens. These results, with a single exception, were 

 recently corroborated by Robinson and Rettger. Cole and 

 Onslow (1916) suggested a pancreatic digestion product of 

 casein as a good medium, and Distaso (1916) succeeded in 

 obtaining good growths of pathogenic organisms in a solution 

 which contained as its only source of nitrogen serum which had 

 been digested with trypsin. 



In the present work solutions of Witte's peptone and of casein 

 were digested with commercial trypsin. The digestion was 

 allowed to continue for five hours at 45°C., after which the 

 liquid was immediately sterilized, and 0.25 per cent beef extract 



